Write Cache Recovery After Loss of Power

1. A method of recovering dirty write cache data after loss of power to a primary controller associated with a write cache, comprising: providing means for retaining information in the write cache in absence of controller power; verifying whether a power down flag stored in the write cache indicates that the write cache was not properly shutdown; verifying whether a configuration ID stored in the write cache matches a configuration ID stored in the controller; verifying whether a configuration sequence number stored in the write cache corresponds to a configuration sequence number stored in the controller; and flushing dirty data present in the write cache to a permanent data storage system when the power down flag indicates that the write cache was not properly shutdown, the configuration ID matches that stored in the primary controller and the configuration sequence number matches the configuration sequence number stored in the primary controller.

2. The method of claim 1 further including incrementing the configuration sequence number stored in the primary controller upon a proper shutdown and storing the configuration sequence number in the write cache if the write cache's configuration ID matches the configuration ID stored in the primary controller.

3. The method of claim 2 further including storing the configuration sequence number in the write cache of a backup controller if the write cache's configuration ID matches the configuration ID stored in the backup controller.

4. The method of claim 2 further including incrementing the configuration sequence number stored in the primary controller upon power up and storing the configuration sequence number in the write cache if the write cache configuration ID matches the configuration ID stored in the primary controller.